parser: Avoid dropping modifiers when splitting list (#8546)

Fix for a linked list usage bug; avoids dropping any modifiers when
moving type modifiers from a linked list of modifiers into their own
linked list. Since this change results in no_diff modifiers to
traditional functions ending up on the return type instead of the
function (due to the order they're parsed in), we duplicate the no_diff
modifier onto the function declaration after the fact.

Includes a test for the original issue. The no_diff redistribution case
is covered by a slangpy device test case.

Fixes #8332

---------

Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

1 files changed, 31 insertions, 0 deletions

diff --git a/tests/autodiff/no-diff-static.slang b/tests/autodiff/no-diff-static.slang
new file mode 100644
index 000000000..15d316a90
--- /dev/null
+++ b/tests/autodiff/no-diff-static.slang
@@ -0,0 +1,31 @@
+//TEST(compute):COMPARE_COMPUTE_EX(filecheck-buffer=BUF):-slang -compute -output-using-type
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<float> outputBuffer;
+// BUF: 1.000000
+// BUF: 1.000000
+
+struct TestStruct : IDifferentiable
+{
+    static const no_diff float foo = 1.0f;
+
+    int x;
+
+    void assignOut()
+    {
+        outputBuffer[0] = foo;
+    }
+}
+no_diff static const float foo = 1.0f;
+
+[shader("compute")]
+[numthreads(1, 1, 1)]
+void computeMain(uint thread_idx: SV_DispatchThreadID)
+{
+    if (thread_idx == 0) {
+        TestStruct t;
+        t.x = 10;
+        t.assignOut();
+    }
+    outputBuffer[1] = foo;
+}